Intravascular stent

ABSTRACT

A stent design reduces the likelihood of contact among structural members when the stent diameter is reduced before insertion into the body. In one approach, an undulating link has a J-shaped profile or has an angled portion on one side at the peak of the link, in order to reduce contact during crimping. The stent may also include structural features that improve such aspects as flexibility, the coatability of a drug coating onto the stent, flare reduction, stent retention within the body and/or reduction of the minimum diameter of the stent during crimping.

This application is a divisional application of U.S. Ser. No. 11/544,256filed Oct. 6, 2006, the entirety of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

The invention relates to vascular repair devices, and in particularintravascular stents, which are adapted to be implanted into a patient'sbody lumen, such as a blood vessel or coronary artery.

Stents are generally tubular-shaped devices that hold open a segment ofa blood vessel or other body lumen such as a coronary artery. They alsoare suitable to support and hold back a dissected arterial lining thatcan occlude the fluid passageway. There are many known stents, such asthose disclosed in U.S. Pat. No. 6,629,994, entitled “IntravascularStent” and issued on Oct. 7, 2003, which is incorporated by referenceherein.

The prior art stents depicted in FIGS. 1-5 have multiplex cylindricalrings connected by one or more undulating links. While some of thesestents are flexible and have the appropriate radial rigidity needed tohold open a vessel or artery, there typically is a tradeoff betweenflexibility, radial strength, and the ability to tightly compress orcrimp the stent onto a catheter. Crimping the stent is important so thatit does not move relative to the catheter or dislodge prematurely priorto controlled implantation in a vessel.

In these prior art stents, each of the cylindrical rings making up thestent has proximal and distal ends, and a cylindrical plane defined by acylindrical outer wall surface that extends circumferentially betweenthe proximal end and the distal end of the cylindrical ring. Generally,the cylindrical rings have a serpentine or undulating shape thatincludes one or more U-shaped elements. The cylindrical rings areinterconnected by at least one undulating link that attaches onecylindrical ring to an adjacent cylindrical ring.

The undulating links may take various configurations but, in general,have an undulating or serpentine shape. The undulating links can includebends connected by substantially straight portions wherein thesubstantially straight portions are substantially perpendicular to thestent longitudinal axis.

The cylindrical rings typically are formed of a plurality of peaks andvalleys, where the valleys of one cylindrical ring are circumferentiallyoffset from the valleys of an adjacent cylindrical ring. In thisconfiguration, at least one undulating link attaches each cylindricalring to an adjacent cylindrical ring so that at least a portion of theundulating links is positioned within one of the valleys and it attachesthe valley to an adjacent peak.

While the cylindrical rings and undulating links generally are notseparate structures, they have been conveniently referred to as ringsand links for ease of identification. Further, the cylindrical rings canoften be thought of as comprising a series of U's, W's and other-shapedstructures in a repeating pattern. Again, while the cylindrical ringsare not divided up or segmented into U's, W's and other shapes, thepattern of the cylindrical rings resemble such configuration. The U's,W's and other shapes promote flexibility in the stent primarily byflexing and by tipping radially outwardly as the stent is deliveredthrough a tortuous vessel.

Although there are many advantages to stents of this type, recentadvances in stent design in which the stent is coated with drugs, raisenew design challenges. It is important that as the stent is crimpedprior to insertion into the body, there is no contact between portionsof the stent. This type of contact, as illustrated in FIGS. 6 and 7, canhave adverse effects on the drug coating which can, for example, form abubble and peel off.

What is needed is a flexible and strong stent having very little or nocontact between structural members as the stent is crimped prior toinsertion into the body. It is also desirable to increase thecoatability of the stent, to reduce flaring, and/or to improve stentretention.

SUMMARY OF THE INVENTION

The present invention includes stent designs that reduce the likelihoodof contact among structural members when the stent diameter is reducedprior to insertion into the body. In one embodiment, a flexibleintravascular stent for use in a body lumen has cylindrical ringsaligned along a common longitudinal axis. The rings are interconnectedto form the stent. Each cylindrical ring has a first delivery diameterfor insertion into the body, and an expanded second diameter after beingimplanted into the body.

At least some of the cylindrical rings have first peaks and secondpeaks. In one embodiment, the second peaks are shorter than the firstpeaks. At least one undulating link attaches each cylindrical ring to anadjacent cylindrical ring. The undulating links have a curved portionthat extends transverse to the longitudinal axis of the stent, towardthe second peak. The height of the second peak is sized so that as thestent is compressed to the first delivery diameter, the curved portionof the undulating link is longitudinally aligned with the second peak.To prevent contact among portions of the stent as the stent is crimpeddown prior to delivery into the body, the stent includes means forpreventing contact between the undulating link and the second peak. This“means” can include an undulating link that has a J-shaped profile, orthat has an angled portion on one side at the peak of the link, and/orother modifications further described in the Detailed Description anddrawings, and their equivalents.

The stent design may also include structural features that improve suchaspects as flexibility, the coatability of a drug coating onto thestent, flare reduction, and stent retention within the body.

Another embodiment prevents structural contact during crimping byutilizing an undulating link that has a special configuration. Aflexible intravascular stent for use in a body lumen has cylindricalrings aligned along a common longitudinal axis and interconnected toform the stent. Each cylindrical ring has a first delivery diameter anda second implanted diameter. At least some of the cylindrical rings havefirst peaks and second peaks, with each of the peaks having a height,the second peaks being shorter than the first peaks. At least oneundulating link attaches each cylindrical ring to an adjacentcylindrical ring. These undulating links have a curved portion extendingtransverse to the stent longitudinal axis toward the second peak. Eachundulating link also has an arm having a first substantially straightportion that is substantially parallel to the longitudinal axis and asecond, angled portion leading to the curve.

Another embodiment further improves retention of the stent within thebody. In this embodiment, a flexible intravascular stent has a pluralityof cylindrical rings aligned along a common longitudinal axis andinterconnected to form the stent. Each cylindrical ring has a firstdelivery diameter and a second implanted diameter. At least some of thecylindrical rings have first peaks and second peaks, each of the peakshaving a height, the second peaks being shorter than the first peaks.The stent also has an end ring having a plurality of first peaks andsecond peaks having a height, the height of the first and second peaksbeing uniform.

Another embodiment of the invention reduces the minimum diameter of thestent when it is crimped, prior to insertion into the body. In thisembodiment, a flexible intravascular stent has a plurality ofcylindrical rings aligned along a common longitudinal axis. At least onelink connects adjacent cylindrical rings. The stent has a proximal endring, which has five symmetric crests of equal height. The stent mayoptionally have different cell designs, with a first cell having twolong crests and one short crest, and a second cell having one long crestand one short crest.

The above and other objects and advantages of this invention will beapparent from the following more detailed description when taken inconjunction with the accompanying drawings of exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view, partially in section, of a prior artstent mounted on a rapid-exchange delivery catheter and positionedwithin an artery;

FIG. 2 is an elevational view, partially in section, similar to thatshown in FIG. 1 wherein the prior art stent is expanded within theartery, so that the stent embeds within the arterial wall;

FIG. 3 is an elevational view, partially in section, showing theexpanded prior art stent implanted within the artery after withdrawal ofthe rapid-exchange delivery catheter;

FIG. 4 is a plan view of a flattened prior art stent which illustratesthe pattern of the stent shown in FIGS. 1-3;

FIG. 5A is a plan view of a flattened stent of one embodiment of theinvention which illustrates the pattern of the rings and links;

FIG. 5B is a partial plan view of the stent of FIG. 6A which has beenexpanded to approximately 3.0 mm inside diameter;

FIG. 5C is a plan view of a portion of the stent of FIG. 6A rolled intoa cylindrical configuration and tightly crimped so that the variousstent struts are either in close contact or contacting each other;

FIG. 6 is a plan view of a prior art stent in a crimped or compressedconfiguration depicting metal-to-metal contact between two portions ofthe stent, thereby causing damage to the drug coating that is on thestent;

FIG. 7 is a plan view of a prior art stent in a crimped or compressedconfiguration depicting even greater metal-to-metal contact between twoportions of the stent than in FIG. 19;

FIG. 8 illustrates one embodiment of the present invention;

FIG. 9 depicts a design that eliminates metal-to-metal contact, allowingthe stent to be crimped without damage to the drug coating;

FIG. 10 is a plan view of a flattened stent of another embodiment of theinvention which illustrates a pattern of the rings and links;

FIG. 11 is an enlarged partial plan view showing modifications to thecell length and bar arm portions of the stent of FIG. 10;

FIG. 12 is an enlarged partial plan view showing modifications to thelong crest portions of the stent of FIG. 10;

FIG. 13 is an enlarged partial plan view showing modifications to thenon-linear link portions of the stent of FIG. 10;

FIG. 14 is an enlarged partial plan view showing modifications to theshort crest portions of the stent of FIG. 10;

FIG. 15 is an enlarged partial plan view showing modifications made tothe Y crest portions of the stent of FIG. 10;

FIG. 16 is a an enlarged partial plan view showing modifications made tothe W crest portions of the stent of FIG. 10;

FIG. 17 is an enlarged partial plan view showing modifications made tothe proximal end ring of the stent of FIG. 10;

FIG. 18 is an enlarged partial plan view showing modifications made tothe distal end ring of the stent of FIG. 10;

FIG. 19 is an enlarged partial plan view illustrating how metal-to-metalcontact is prevented as a result of the stent design; and

FIG. 20 is a plan view of a flattened stent of another embodiment of theinvention which illustrates a pattern of the rings and links.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning to the drawings, FIG. 1 depicts a prior art stent 10 mounted ona conventional catheter assembly 12. The assembly 12 is used to deliverand implant the stent in a body lumen, such as a coronary artery,peripheral artery, or other vessel or lumen within the body. Thecatheter assembly includes a catheter shaft 13 which has a proximal end14 and a distal end 16. The catheter assembly is configured to advancethrough the patient's vascular system over a guide wire by any of thewell known methods of an over the wire system (not shown) or by a wellknown rapid exchange catheter system, such as the one shown in FIG. 1.

Catheter assembly 12 as depicted in FIG. 1 is of the well known rapidexchange type which includes an RX port 20 where the guide wire 18 willexit the catheter. The distal end of the guide wire 18 exits thecatheter distal end 16 so that the catheter advances along the guidewire on a section of the catheter between the RX port 20 and thecatheter distal end 16. As is known in the art, the guide wire lumenthat receives the guide wire is sized for receiving various diameterguide wires to suit a particular application. The stent is mounted onthe expandable member 22 (balloon) and is crimped tightly thereon sothat the stent and expandable member present a low profile diameter fordelivery through the arteries.

As shown in FIG. 1, a partial cross-section of an artery 24 is shownwith a small amount of plaque that has been previously treated by anangioplasty or other repair procedure. Stent 10 is used to repair adiseased or damaged arterial wall which may include the plaque 26 asshown in FIG. 1, or a dissection, or a flap which are sometimes found inthe coronary arteries, peripheral arteries and other vessels.

In a typical procedure to implant prior art stent 10, the guide wire 18is advanced through the patient's vascular system by known methods sothat the distal end of the guide wire is advanced past the plaque ordiseased area 26. Prior to implanting the stent, the cardiologist maywish to perform an angioplasty procedure or other procedure (i.e.,atherectomy) in order to open the vessel and remodel the diseased area.Thereafter, the stent delivery catheter assembly 12 is advanced over theguide wire so that the stent is positioned in the target area. Theexpandable member or balloon 22 is inflated by well known means so thatit expands radially outwardly and in turn expands the stent radiallyoutwardly until the stent is apposed to the vessel wall. The expandablemember is then deflated and the catheter withdrawn from the patient'svascular system. The guide wire typically is left in the lumen forpost-dilatation procedures, if any, and subsequently is withdrawn fromthe patient's vascular system. As depicted in FIGS. 2 and 3, the balloonis fully inflated with the prior art stent expanded and pressed againstthe vessel wall, and in FIG. 3, the implanted stent remains in thevessel after the balloon has been deflated and the catheter assembly andguide wire have been withdrawn from the patient.

The prior art stent 10 serves to hold open the artery after the catheteris withdrawn, as illustrated by FIG. 3. Due to the formation of thestent from an elongated tubular member, the undulating components of thestent are relatively flat in transverse cross-section, so that when thestent is expanded, it is pressed into the wall of the artery and as aresult does not interfere with the blood flow through the artery. Thestent is pressed into the wall of the artery and will eventually becovered with endothelial cell growth which further minimizes blood flowinterference. The undulating portion of the stent provides good tackingcharacteristics to prevent stent movement within the artery.Furthermore, the closely spaced cylindrical elements at regularintervals provide uniform support for the wall of the artery, andconsequently are well adapted to tack up and hold in place small flapsor dissections in the wall of the artery, as illustrated in FIGS. 2 and3.

One of the problems associated with some prior art stents such as theone shown in FIG. 4, is the ability to more tightly crimp or compressthe stent 10 onto the balloon portion of the catheter. For example, theundulating portion 27 of the links 28 of the prior art stent in FIG. 4are positioned between two struts 29A/29B so that as the stent istightly crimped or compressed onto the balloon portion of the catheter,the struts can only come so close to the undulating portion beforecontact is made.

Other Prior Art Designs

FIGS. 5A-5C depict a stent 30 in various configurations. Referring toFIG. 5A, for example, stent 30 is shown in a flattened condition so thatthe pattern can be clearly viewed, even though the stent is in acylindrical form in use, such as shown in FIG. 5C. The stent istypically formed from a tubular member. However, it can be formed from aflat sheet such as shown in FIG. 5A and rolled into a cylindricalconfiguration as shown in FIG. 5C.

Each cylindrical ring 40 defines a cylindrical plane 50 (FIG. 5C) whichis a plane defined by the proximal and distal ends 46, 48 of the ringand the circumferential extent as the cylindrical ring travels aroundthe cylinder. Each cylindrical ring includes cylindrical outer wallsurface 52 defining the outermost surface of the stent, and cylindricalinner wall surface 53 defining the innermost surface of the stent.Cylindrical plane 50 follows the cylindrical outer wall surface.

Undulating link 54 is positioned within cylindrical plane 50. Theundulating links connect one cylindrical ring 30 to an adjacentcylindrical ring 30 and contribute to the overall longitudinalflexibility to the stent due to their unique construction. Theflexibility of the undulating links derives in part from curved portion56 connected to straight portions 58 wherein the straight portions aresubstantially perpendicular to the longitudinal axis of the stent. Thus,as the stent is being delivered through a tortuous vessel, such as acoronary artery, the curved portions 56 and straight portions 58 of theundulating links will permit the stent to flex in the longitudinaldirection which substantially enhances delivery of the stent to thetarget site.

As shown in FIGS. 5A-5C, each of the cylindrical rings has a pluralityof first peaks 60 which have first struts 66 attached to a first apex67. The cylindrical rings also have second peaks 61 which have secondstruts 68 attached to a second apex 69. The length of the second struts68 is typically shorter than the length of the first struts 66. As canbe seen in FIG. 5C, when the stent is in a crimped condition, or apartially crimped condition, the first struts and second strutsrespectively will be closer to each other when the stent is compressedor crimped onto the balloon or expandable member of the catheter.

Referring to FIGS. 5A-5C, the stent 30 can be described as havingcylindrical rings formed of U-shaped portions 70, portions 72, andW-shaped portions 74. Again, while the stent is generally laser cut froma tube and it typically has no discreet parts, for ease ofidentification the stent of the invention also can be referred to ashaving U- and W-shaped portions, as appropriate for the embodiment. TheU-shaped portions have no supporting structure attached thereto. The Wportion has at its base or curve portion an arm 78 which attaches at theother end of the undulating link. The length of the arms attaching thelinks to the rings and shape can vary.

The stent 30 can be mounted on a balloon catheter similar to that shownin the prior art device in FIG. 1. The stent is tightly compressed orcrimped onto the balloon portion of the catheter and remains tightlycrimped onto the balloon during delivery through the patient's vascularsystem. When the balloon is expanded, the stent expands radiallyoutwardly into contact with the body lumen, for example, a coronaryartery. When the balloon portion of the catheter is deflated, thecatheter system is withdrawn from the patient and the stent remainsimplanted in the artery. Similarly, if the stent of the presentinvention is made from a self-expanding metal alloy, such asnickel-titanium or the like, the stent may be compressed or crimped ontoa catheter and a sheath (not shown) is placed over the stent to hold itin place until the stent is ready to be implanted in the patient. Suchsheaths are well known in the art. Further, such a self-expanding stentmay be compressed or crimped to a delivery diameter and placed within acatheter. Once the stent has been positioned within the artery, it ispushed out of the catheter or the catheter is withdrawn proximally andthe stent held in place until it exits the catheter and self-expandsinto contact with the wall of the artery. Balloon catheters andcatheters for delivering self-expanding stents are well known in theart.

Coating the Stent with Drugs

Stents can also be coated with a drug or therapeutic agent to assist inrepair of the bifurcated vessel and may be useful, for example, inreducing the likelihood of the development of restenosis. Further, it iswell known that the stent (usually made from a metal) may require aprimer material coating to provide a substrate on which a drug ortherapeutic agent is coated, since some drugs and therapeutic agents donot readily adhere to a metallic surface. The drug or therapeutic agentcan be combined with a coating or other medium used for controlledrelease rates of the drug or therapeutic agent. Examples of therapeuticagents that are available as stent coatings include rapamycin,ererolimus clobetasol, actinomycin D (ActD), or derivatives and analogsthereof. ActD is manufactured by Sigma Aldrich, 1001 West Saint PaulAvenue, Milwaukee, Wis. 53233, or COSMEGEN, available from Merck.Synonyms of actinopmycin D include dactinomycin, actinomycin IV,actinomycin 11, actinomycin X1, and actinomycin C1. Examples of agentsinclude other antiproliferative substances as well as antineoplastic,antinflammatory, antiplatelet, anticoagulant, antifibrin, antithomobin,antimitotic, antibiotic, and antioxidant substances. Examples ofantineoplastics include taxol (paclitaxel and docetaxel). Examples ofantiplatelets, anticoagulants, antifibrins, and antithrombins includesodium heparin, low molecular weight heparin, hirudin, argatroban,forskolin, vapiprost, prostacyclin and prostacyclin analogs, dextran, Dphe pro arg chloromethylketone (synthetic antithrombin), dipyridamole,glycoprotein, 11b/111a platelet membrane receptor antagonist,recombinant hirudin, thrombin inhibitor (available from Biogen), and 7E3B® (an antiplatelet drug from Centocore). Examples of antimitoticagents include methotrexate, azathioprine, vincristine, vinblastine,fluorouracil, adriamycin, and mutamycin. Examples of cytostatic orantiproliferative agents include angiopeptin (a somatostatin analog fromIbsen), angiotensin converting enzyme inhibitors such as Captopril(available from Squibb), Cilazapril (available from Hoffman LaRoche), orLisinopril (available from Merck); calcium channel blockers (such asNifedipine), colchicine fibroblast growth factor (FGF) antagonists, fishoil (omega 3 fatty acid), histamine antagonist, Lovastatin (an inhibitorof HMG-CoA reductase, a cholesterol lowering drug from Merck),monoclonal antibodies (such as PDGF receptors), nitroprusside,phosphodiesterase inhibitors, prostaglandin inhibitor (available fromGlazo), Seramin (a PDGF antagonist), serotonin blockers, steroids,thioprotease inhibitors, triazolopyrimidine (a PDGF antagonist), andnitric oxide. Other therapeutic substances or agents which may beappropriate include alpha-interferon, genetically engineered epithelialcells, and dexamethasone.

It should be understood that any reference in the specification orclaims to a drug or therapeutic agent being coated on the stent is meantthat one or more layers can be coated either directly on the stent oronto a primer material on the stent to which the drug or therapeuticagent readily attaches.

Stent Design for Reducing Contact and Protecting the Drug Coating

Considering particular problems that may arise with some prior artstents, FIG. 6 illustrates a stent that has been crimped prior todelivery within the body. The short crest 61 is seen in FIG. 6 to be incontact with a middle connector of the crest 74. In particular, aportion of the short crest 61 is in interference with a metal member 74,such that any drug coating that is on the respective points of contactmay be damaged.

An even more serious situation is illustrated in FIG. 7. In thisscenario, the non-linear link 54 is also in contact with the short crest61. In this case, the short crest 61 is nested in between the non-linearlink 54 and the respective middle connector of the crest 74.Consequently, there are two points of metal-to-metal contact. In thescenario of FIG. 7, even more of the drug coating on the stent isdamaged in this crimped configuration.

At this juncture, it is noted that the term “metal-to-metal contact” isa term of convenience. The phrase refers to two portions of the stentcoming into contact when the stent is crimped. However, “metal-to-metalcontact” as used herein may also apply to stents that are made ofmaterials other than metal, such as stents that are made from a polymeror materials to be developed in the future.

It is a considerable challenge to design a stent pattern that will avoidmetal-to-metal contact. By creating such a design, the problems thatarise with damage to the drug coating from metal-to-metal contact can beeliminated. Consequently, the drug coating may maintain its integrity,and function as a drug eluting coating for the desired period of time.

Considering now an embodiment of the present invention, for example,FIG. 8 illustrates a stent pattern in which the short crest 161 ismodified. In particular, the prior design is shown in dotted lines,whereas the new design that has been modified is shown in solid lines.With the modified short crest 161, the upward angulation is changed suchthat the short crest is lifted upward compared to the original shortcrest design. At the same time, the non-linear link 154 is modified tohave more of a “J” shaped configuration. This combination of a shortcrest having a modified upward angulation with a modified, “J” shapednon-linear link 154 results in a stent design that can be crimpedwithout suffering the metal-to-metal contact illustrated in FIGS. 6 and7. Indeed, FIG. 9 illustrates the stent pattern of FIG. 8 when thecorresponding stent is in a crimped configuration. In thisconfiguration, the short crest 161 does not come into contact with acorresponding portion of the W crest, or with the corresponding linearlink 154. The integrity of the drug coating is therefore maintained,such that the drug coating is not damaged during crimping.

Turning to a second modified design, FIG. 10 illustrates anotheralternative stent pattern designed to reduce metal-to-metal contact. Thedesign of FIG. 10 also results in increased flexibility, improvedcoatability, and better stent retention within the body as compared tothe design in FIG. 5A. Specific features that have been modified in thedesign of FIG. 10, which will be discussed in greater detail below,include a modified non-linear link 254, a modified long crest 260, amodified short crest 261, a modified crest 272, and a modified W crest274. Also, in one of the embodiments, the proximal end ring 292 ischanged such that all of the crests, including both the short crests andthe long crests, are of uniform length. The modification to the proximalend ring 292 can be seen when compared with the distal end ring 290, inwhich the short and long crests, 261 and 260, have different lengths.

FIG. 11 illustrates two modified aspects of the stent design, asillustrated in FIG. 10. The first aspect relates to the cell length,which is a measure of the distance between rings. For example, thedistance 298 in the design of FIG. 11 is greater than the correspondingcell length in the design of FIG. 5A. This longer cell length has beendetermined to improve the flexibility of the stent within the body. Atthe same time, the bar arms in FIG. 11 are seen to be less filleted ascompared to the corresponding bar arms in the design of FIG. 5A. Theseless filleted bar arms help to reduce metal-to-metal contact duringcrimping. Again, it is noted in FIGS. 11-18 that the new design is shownin solid black line, whereas the old design is shown in broken line.

Considering FIG. 12, the long crest 260 is shown now to be angled awayfrom the non-linear link. In one embodiment, the long crest is angledaway from the non-linear link by approximately 6.5 degrees. Of course,other angles may be used as desired. This angling away from thenon-linear link also contributes to reducing metal-to-metal contact whenthe stent is crimped.

FIG. 13 illustrates a non-linear link that is taller and wider than itscorresponding non-linear link in the design of FIG. 5A. This taller andwider non-linear link 254 helps to improve the flexibility of themodified stent. The non-linear link 254 is also shown to be angled. Thisangling helps to reduce metal-to-metal contact when the stent iscrimped.

FIG. 14 illustrates a modification that may be made to the short crest261. The short crest is slightly shorter than the corresponding shortcrest of FIG. 5A. Also, the short crest radii is somewhat increased ascompared to the original design. The increased radii of the short crest261 may help to improve coatability of the stent. That is, the greaterradii helps reduce what is known in the art as “webbing.” Webbing is awell known problem in which the drug coating in certain regions of thestent becomes non-uniform. Consequently, by increasing the radius, thelikelihood of webbing is decreased.

Turning to the crest 272 of FIG. 15, the crest radius is increasedsomewhat as compared to the original design of FIG. 5A. Again, thislarger radius helps improve the coatability of the stent. The drugcoating on the larger radius is less likely to web, thereby helping tofoster more uniform distribution of the drug after deployment within thebody.

FIG. 16 illustrates a modification to the W crest 274. The Wconfiguration is more “open” than in the previous designs. This moreopen W crest 274 also helps to reduce the likelihood of webbing, andimprove the coatability of the stent.

FIG. 17 illustrates a proximal end ring 292. As can be seen by comparingthe solid lines with the broken lines of the previous configuration, themodified proximal end ring is somewhat wider than the original design.This additional width helps to foster better stent retention once thestent is deployed. It is also noted that no W crest is used in thisproximal end ring. The pattern of all crests in the proximal end ringhaving a uniform length, helps to improve stent retention within thevessel.

FIG. 18 illustrates a portion of the distal end ring 290, in which thedistal end ring 290 is somewhat wider than the corresponding distal endring in the design of FIG. 5A. Also, the long crest 260 is wider in thecrest region on the distal end ring 290 of the modified design, than inthe original.

The foregoing combination of features leads to a stent design having anumber of improved properties. One such property is increasedflexibility, while others include improved coatability and reducedlikelihood of webbing. A further improved property is better stentretention, as a result of modifications to the proximal end ring 292.Most importantly, the modified stent design of FIG. 10 reduces thelikelihood of metal-to-metal contact, thereby protecting the integrityof the drug coating on the stent and improving drug delivery within thebody.

FIG. 19 illustrates the stent of FIG. 10 as it appears in the crimpedconfiguration. As can be seen in FIG. 19, there is no metal-to-metalcontact and consequently no damage to the drug coating when the stent iscrimped. As can be seen in FIG. 19, the non-linear link 252, having theangled upper portion, stays comfortably away from the corresponding tipof the adjacent short crest.

In summary, the modifications illustrated in FIGS. 10-19 can becategorized as follows. The following features help to improveflexibility of the stent: longer cell length, and taller and widernon-linear links. The following features can be said to reducemetal-to-metal contact: the long crest being angled away from thenon-linear link, the angled non-linear link having two different bendsas opposed to a rounded non-linear link with symmetric bends, and lessfilleted bar arms. The following features help to improve coatabilityand reduce the likelihood of webbing: a larger short crest radii, alarger crest radii, more open W crest radii. Additional effects ofmodifications made in FIGS. 10-19 include less likelihood of flaringwith the uniform proximal end ring 292 in which there is no W crest inthe proximal end ring. Also, the wider proximal and distal end ringshelp to improve stent retention.

It is noted that in the context of this patent application. There arevarious “means” for accomplishing important design functions of thestent. The following is a non-limiting recital of different “means”disclosed herein. It should be understood that this list isnon-limiting, and that particular “means” may include additionalfeatures and/or combinations of features other than those listed below.“Means for improving flexibility” refers to a longer cell length, and/ortaller and wider non-linear link. “Means for reducing contact” refers tothe long crest being angled away from the non-linear link, the anglednon-linear link with two different bends as opposed to a roundednon-linear link with symmetric bends, for example, a non-linear linkhaving a “J” shape profile, and/or less filleted bar arms as compared tothe design of FIG. 65A. “Means for improving coatability” refers to thelarger short crest radius, the larger crest radius, and a more open Wcrest radius. “Means for reducing flaring” refers to an end ring designin which all of the crests are uniform in length and in which there isno W crest in the end ring. Finally, “means for improving stentretention” refers to wider proximal and/or wider distal end rings.

Stent Having a Proximal End Ring with Five Symmetric Crests

A further improvement to stent design may be made in order to reduce thediameter of the stent when it is crimped. In this approach, one crestfrom the proximal end ring is removed so that there is less material tocrimp down. In particular, the stent design of FIG. 33 has fivesymmetric crests on the end ring 392 instead of six crests. Also, thereare only two non linear links 354, 355 in the proximal end ring of thisdesign.

The distal end ring 390, by contrast, has a “W” crest 374, andcorresponding long and short crests. In one alternative embodiment, thedistal end ring 390 may have the same structure as the proximal end ring392, although the embodiment of FIG. 20 as illustrated has differentstructures for the distal and proximal end rings.

A further improvement relates to the cell structure of the stent of FIG.20. In one cell 396, there are two long crests 359, 360 and one shortcrest 361. In the second cell, there is one long crest 399 and one shortcrest 400. This is in contrast to the design of FIG. 5A, for example, inwhich there is one long crest and one short crest per cell. The nonlinear link in the design of FIG. 20 (e.g. 354) is also somewhatsmaller, to allow more room for crimping to a smaller diameter.

In light of the foregoing, “means for reducing minimum crimp diameter”refers to the five symmetric crest design and structural equivalentsthereof.

Methods of Stent Manufacture

A stent according to the present invention can be made in many waysknown in the art. As non-limiting examples, methods of manufacturingstents are described in U.S. patent application Ser. No. 10/946,223,entitled, “Pulsed Fiber Laser Cutting System For Medical Implants,”published as Publication No. US 2005/0035101, and in U.S. patentapplication Ser. No. 11/278,131, entitled, “Pulsed Synchronized LaserCutting Of Stents” filed on Mar. 30, 2006, both of which areincorporated by reference herein. Similarly, U.S. Pat. No. 6,521,865,issued on Feb. 18, 2003 and entitled, “Pulsed Fiber Laser Cutting Systemfor Medical Implants,” is also incorporated by reference herein.

Materials from which a Stent May be Made

The stent of the present invention can be made from any of a widevariety of stent materials known in the art. As non-limiting examples,such materials may include stainless steel, cobalt, chromium, tantalum,titanium, nickel-titanium, nickel-titanium-vanadium, Elgiloy®, andvarious polymers. While stainless steel is often used, many othermaterials, such as shape memory alloys or polymers may be used. Shapememory alloys are well known and include, but are not limited to,nickel-titanium and nickel-titanium-vanadium. Any of the shape memoryalloys can be formed into a tube and laser cut in order to form thepattern of the stent of the present invention. As is well known, theshape memory alloys of the stent of the present invention can includethe type having superelastic or thermoelastic martensitictransformation, or display stress-induced martensite.

Importantly, a stent formed of shape memory alloys, whether thethermoelastic or the stress-induced martensite-type, can be deliveredusing a balloon catheter of the type described herein, or be deliveredvia a catheter without a balloon or a sheath catheter.

CONCLUSION

While the invention has been illustrated and described herein, in termsof its use as an intravascular stent, it will be apparent to thoseskilled in the art that the stent can be used in other body lumens.Further, particular sizes and dimensions, number of undulations orU-shaped portions per ring, materials used, and the like have beendescribed herein and are provided as examples only. It is further notedthat while many different structural aspects have been discussed herein,the invention relates both to structural aspects as considered alone, aswell as two or more aspects in combination. That is, it is to beemphasized that the invention resides in various combinations ofelements, as outlined in the claims. Other modifications andimprovements may be made without departing from the scope of theinvention.

We claim:
 1. A flexible intravascular stent for use in a body lumen,comprising: a plurality of cylindrical rings aligned along a commonlongitudinal axis and interconnected to form the stent, each cylindricalring having a first delivery diameter and a second implanted diameter;at least some of the cylindrical rings each having a plurality of firstpeaks and second peaks, each of the peaks having a height, the secondpeaks being shorter than the first peaks; at least one undulating linkattaching each cylindrical ring to an adjacent cylindrical ring, atleast one undulating link having a J-shaped portion which includes afirst curve that has a radius greater than a radius of the second peak,so that the J-shaped portion is prevented from contacting the secondpeak radius when the stent is compressed to the first delivery diameter.2. The stent of claim 1, wherein the stent is formed from a shape memoryalloy.
 3. The stent of claim 1, wherein the stent is formed from asuperelastic or pseudoelastic metal alloy.
 4. The stent of claim 1,wherein at least a portion of the stent has a variable thicknessconfiguration.
 5. The stent of claim 1, wherein at least some of thefirst peaks have a first radius and the second peaks have a secondradius, the second radius being greater than the first radius.
 6. Thestent of claim 1, wherein at least some of the first peaks have a pairof first struts and at least some of the second peaks have a pair ofsecond struts, the first struts being longer than the second struts. 7.The stent of claim 1, wherein the stent further comprises a short cresthaving an upward angulation.
 8. The stent of claim 1, wherein the stentfurther comprises means for improving flexibility of the stent.
 9. Thestent of claim 1, wherein the stent further comprises means forimproving coatability of a drug coating onto the stent.
 10. The stent ofclaim 1, wherein the stent further comprises means for reducing flaring.11. The stent of claim 1, wherein the stent further comprises means forimproving stent retention.